ISO 13728:2020

Overview

ISO 13728:2020 - "Ships and marine technology - Ship's mooring and towing fittings - Panama chocks" specifies design, material, manufacturing, inspection and marking requirements for Panama chocks used to lead mooring and towing ropes. Intended primarily for ships transiting the Panama Canal, the standard covers both deck‑mounted (Type A) and bulwark‑mounted (Type B) chocks in nominal opening sizes 310 mm and 360 mm, and defines safe working load (SWL) practices compatible with canal and normal mooring operations.

Key topics and requirements

• Types & sizes
  • Type A: deck‑mounted; Type B: bulwark‑mounted.
  • Nominal opening widths: 310 and 360 mm.
• Materials
  • Steel casting with yield point ≥ 235 N/mm²; carbon ≤ 0.23% for weldability.
• Load & strength assessment
  • Load cases include individual horizontal and vertical loadings (not assumed simultaneous).
  • Annex A gives the basis for strength assessment, including bearing radii, opening area minima and FEM analysis rules.
  • Stress criterion: combined stress limited to 85% of material yield under SWL.
• SWL (safe working load)
  • Example reference SWLs are provided (e.g., ~48 t, 70 t, 79 t depending on type/size), but the standard notes these are reference values; actual SWL must account for foundation and under‑deck reinforcement and be recorded in the ship’s mooring/towing plan.
• Construction & manufacture
  • Foundations and weld connections must transmit maximum loading without plastic deformation or cracking.
  • Surfaces contacting ropes must be smooth; all surfaces free from visible flaws.
  • External anti‑corrosion coating required; minimum radii for unspecified edges ≥ 25 mm.
• Marking & documentation
  • SWL must be shown on the towing and mooring plan (per IMO MSC/Circ.1175) and marked on the chock or foundation in tonnes.

Applications and users

ISO 13728:2020 is used for:

• Shipbuilders and outfitting contractors specifying and installing ship mooring fittings.
• Manufacturers of Panama chocks and deck hardware.
• Naval architects and marine engineers designing under‑deck reinforcement and foundations.
• Shipowners, ship operators, classification societies and Panama Canal authorities verifying compliance for vessels transiting locks.
• Maintenance and inspection teams ensuring safe operation and correct SWL marking.

Practical use cases include selection of chock types for lock transits, design verification using FEM per Annex A, factory inspection criteria and on‑board marking and documentation for mooring/towing plans.

Related standards and references

• ISO 13729 (closed chocks for larger vessels / Panamax Plus & Neopanamax)
• ISO 4990 (steel castings requirements)
• IMO MSC/Circ.1175 (guidance on shipboard towing and mooring equipment)
• Panama Canal Requirements - OP Notice to shipping No. N‑1‑2019
• IACS UR A2, OCIMF MEG4

Keywords: ISO 13728:2020, Panama chocks, ship mooring fittings, safe working load (SWL), Panama Canal, deck-mounted chock, bulwark-mounted chock, marine technology.